The subject matter of the present invention is a device and a method for testing tablets. Within the context of quality control of tablets it is necessary to test tablets for properties such as length, width, breaking resistance and weight. The Deutsche Arzneibuch (German Pharmacopoeia) contains the relevant legal regulations. This process should, if possible, be carried out automatically, so that a large number of tablets can be tested within a short period of time. Moreover, it has to be ensured that tablets of different shapes and sizes can be correctly positioned in order to allow an error-free measurement to be carried out. The prior art includes a number of devices and methods that are suitable for this purpose.
German Patent Document DE 197 33 436 C2 describes a tablet testing device for testing oblong tablets. Here, the tablets to be tested are initially fed to weighing scales by a feeding device and are subsequently transferred to a transport device by the latter. On the transport device, the tablets are deposited in a predefined position, so that further tests can be carried out. The correct orientation of the tablets as they are deposited on the transport device is here achieved by means of the fact that the scales pan has a bottom in the form of a gutter. This ensures that the oblong tablets are correctly orientated. Moreover, a stumbling block, such as a wedge, may be located on the transport device, which is provided for cases where the tablet falls onto the transport device head first. In this case, the stumbling block ensures that the tablet tilts onto its long side. According to this invention, a correct orientation of a tablet is effected, however, the tablet is exposed to site considerable forces during its transfer through the gutter, which could cause them to be damaged.
German Patent Document DE 10 2006 004 215 B4 discloses a break resistance testing device for tablets of different shapes and sizes. In order to realise the orientation of the tablets, two centering rollers are used, which are driven in opposite directions and are arranged next to each other. If an oblong tablet is placed on the rollers, the rotation of the latter ensures that the oblong tablet orientates itself in the longitudinal direction between the rollers. Subsequently, the resistance may be tested by means of a breaking jaw. In order to ensure that tablets of different shapes and sizes can be orientated, the device is equipped with a pivotable positioner that can orientate the rollers differently. The orientation process is carried out quickly, however, due to the use of rollers it may be difficult to clean the apparatus after a break resistance test.
Utility Model DE 298 24 199 U1 discloses a system for carrying out hardness tests on specimens, which adopts an alternative approach. Here, the tablet is placed on a test table, but no orientation of the tablet is carried out after that. Instead, the orientation of the specimen is determined by means of a device for position detection. Subsequently, a pressure piston as well as a counter bearing, which are used for hardness testing of the tablet, are appropriately orientated so that the testing of the tablet can be carried out. However, this invention requires a complex and cost-intensive design that must comprise means for image detection.
PCT Publication WO 2013/061223 A2 discloses a method and a device for checking tablets, which orientates the tablets with the aid of a pivotable rocker. The tablet is here deposited on the initially horizontal rocker, which now carries out a pivoting movement. As a result of the effect of gravity and the pivoting movement it is achieved that the tablet orientates itself on a positioning surface. The positioning surface has here a concave shape that extends along the shape defined by the movement of the rocker. In order to support the correct orientation of the tablet, the pivotable rocker may additionally be inclined, at an angle to the positioning surface, or may have an additional device on the side that is opposite the positioning surface, which carries out a pre-orientation of the tablet. Once the rocker has been positioned and returned into a horizontal position, the tablet is tested. Since the positioning is here carried out under the effect of gravity and the rocking movement has to be carried out at a sufficient speed, the risk that the forces acting on the tablet during the orientation process might be too high cannot be eliminated here either.
The device according to the invention preferably comprises a rotary disc (1), a first positioning surface (2a), a further positioning surface (3a), a breaking jaw (4), a transport rail (5), a rake (6a) and a tablet (7), wherein the tablet (1) is located, in this view, on the transport rail (5) (FIG. 1). If the rake (6a) is a transport rake (6), then the latter can transport the tablet (7) onto the rotary disc (1).
A tablet (7), preferably an oblong tablet, is deposited on the rotary disc (1). The tablet (7) comes into contact with a first positioning surface (2a), which is preferably an abutment (2), as a result of the rotation of the rotary disc (1) in a first direction, and is orientated thereon. The orientation of the tablet (7) is carried out as a result of the fact that the latter comes into contact with a positioning plane as a result of the rotation of the rotary disc and is orientated on this positioning plane as a result of the rotation of the rotary disc along the longitudinal axis thereof. The rotation of the rotary disc (1) can here be carried out as early as prior to the tablet being deposited on the rotary disc, or may not start until after the tablet is located on the rotary disc. Subsequently, at least one test of the tablet (7) is carried out. In order to carry out a further test, the tablet (7) is positioned for testing in a further position as a result of the fact that the rotary disc rotates in a direction opposite to the direction of the previous rotation, so that the tablet (7) is orientated along a positioning surface (3a), which is preferably a stop (3).
In a preferred embodiment of the device, a rake (6a) is provided which pushes the tablet material from the rotary disc (1) once the test is completed. If the rake (6a) is a transport rake (6), the latter can push the tablet (7) onto the rotary disc (1) prior to the test. Thus, the transport rake (6) can both transport the tablet onto the rotary disc (1) and push the tablet (7) or tablet residues from the rotary disc (1) once the test is complete.
A preferred method for testing tablets according to the present invention will be described below with reference to FIGS. 2 to 4. In the initial condition, the tablet (7) is located on a transport rail (5). The singling of the tablets has been carried out in a previous step, so that always only one tablet (7) at a time is located on the transport rail (5). The transport rake (6) will now carry out, supported by a motor, a movement in the direction of the rotary disc (1) and as a result pushes the tablet (7) onto the rotary disc (1). The transport rake (6) moves from the rotary disc (1) in the direction of its starting position, but only so far that it is no longer positioned over the rotary disc (1). As soon as the tablet (7) reaches the rotary disc (1), the rotary disc (1) starts a motor-supported rotation in the counter-clockwise direction. As a result, the tablet (7) is positioned along the abutment (2).
Whilst a rotary disc (1) continues to rotate in the counter-clockwise direction, the breaking jaw (4) is moved in the direction of the abutment (2) until a predefined counterforce occurs. The distance travelled is recorded by a computing unit that is integrated into the testing device and is also used for controlling the movements of the device. This method step is shown in FIG. 3. Due to the orientation of the tablet (7), its width is determined thereby.
Subsequently, the breaking jaw (4) moves back into its starting position and the rotary disc (1) starts to rotate in the clockwise direction. As a result, the tablet (7) is orientated on the stop (3). This method step is shown in FIG. 4. The rotary disc (1) continues its rotation, whilst the breaking jaw moves in the direction of the abutment (2). The movement of the breaking jaw (4) is suspended as soon as the predefined counterforce occurs on the breaking jaw (4). The distance travelled is recorded by the computing unit. Due to the orientation of the tablet (7), the length of the tablet (7) can be determined on the basis of the distance travelled. The breaking jaw (4) remains in its current position and now exerts a force in the direction of the abutment (2), which is linearly increased. As soon as the tablet (7) breaks, the force exerted at that point is recorded by the computing unit. The rotary disc (1) terminates its rotation and the breaking jaw (4) is moved back into its starting position.
Subsequently, the transport rake (6) moves in the direction of the stop and as a result pushes the residues of the tablet (7) from the rotary disc (1). In the course of this, the transport rake (6) impinges on the stop (3). Since it is fixed to a rotary joint (8), the stop (3) yields to the transport rake (6). The transport rake (6) now returns into its starting position. In the course of this, also the stop (3) resumes its starting position, which is brought about by a spring integrated in the rotary joint. A further tablet (7) can now be placed on the transport rail (5), so that the process can be restarted.